Polyethylene terephthalate filaments and yarns are utilized in a wide variety of applications. For instance, polyethylene terephthalate (PET) is commonly used in manufacturing high modulus industrial yarns. It is generally desirable for such industrial yarns to have the highest modulus and highest strength possible. This is because such yarns are utilized in making reinforcing elements for various products, such as tires, belts and hoses, where high strength and high modulus is beneficial.
The filaments utilized in making industrial yarns are typically made by melt spinning. In such procedures the melt spun filaments are subsequently drawn and thermally treated to enhance mechanical properties, such as modulus and strength. The PET utilized in commercial melt spinning procedures has conventionally had an intrinsic viscosity of less than about 1.0 dl/g. Until recently the possibility of utilizing PET having higher intrinsic viscosity was not a viable option. This was simply because viable commercial sources for PET having such high intrinsic viscosities were not available. However, recent advances in the art of preparing PET have made sources of PET having intrinsic viscosities of greater than 3.0 dl/g a viable option. However, standard melt spinning techniques cannot beneficially utilize ultra-high molecular weight PET having an intrinsic viscosity of greater than about 1.0 dl/g.